Retrieval systems and methods for use thereof

ABSTRACT

The devices and methods described herein relate to improved structures for removing obstructions from body lumens. Such devices have applicability in through-out the body, including clearing of blockages within the vasculature, by addressing the frictional resistance on the obstruction prior to attempting to translate and/or mobilize the obstruction within the body lumen.

RELATED APPLICATIONS

This application is continuation of PCT Application PCT/US2012/039216,publication WO2012/162437, filed May 23, 2012 entitled RETRIEVAL SYSTEMSAND METHODS FOR USE THEROF which is a non-provisional of U.S.Provisional Application Nos. 61/489,183 filed May 23, 2011 entitledRETRIEVAL SYSTEMS AND METHODS FOR USE THEROF, PCT/US2012/039216,publication WO2012/162437 is also a non-provisional of U.S. ProvisionalApplication No. 61/489,254 filed May 24, 2011 entitled STENT RETRIEVERWITH INTEGRATED PROTECTION the entirety of each of which is incorporatedby reference.

FIELD OF THE INVENTION

The devices described herein are intended to retrieve obstructions fromthe body. Such devices have applicability throughout the body, includingclearing of blockages within body lumens and providing passiveprotection of such, such as the vasculature, by providing a capturingportion that can translate and/or mobilize the obstruction within thebody lumen.

BACKGROUND OF THE INVENTION

A large number of medical procedures require the use of medicaldevice(s) to remove an obstruction from a body lumen, vessel, or otherorgan. An inherent risk in such procedures is that mobilizing orotherwise disturbing the obstruction can potentially create further harmif the obstruction or a fragment thereof dislodges from the retrievaldevice. If a particle or the obstruction breaks free from the device andflows downstream, it is highly likely that the particle or obstructionwill become trapped in smaller and more tortuous anatomy. In many cases,the physician will no longer be able to use the same retrieval device toagain remove the obstruction because the size of the device may preventadvancing the device to the site of the new obstruction.

Even in successful procedures, a physician must proceed with caution toprevent the walls of the vessel or body lumen from imparting undesiredforces to shear or dislodge the obstruction as it is translated throughthe body during removal. These forces have the potential of breakingportions or fragments of the obstruction away. In some cases, theobstruction can simply break free from the retrieval device and canlodge in a new area causing more concern than the original blockage.

Procedures for restoring flow within the cerebral vasculature as aresult of ischemic stroke are one example of where these issues presenta concern. The brain relies on its arteries and veins to supplyoxygenated blood from the heart and lungs and to remove carbon dioxideand cellular waste from brain tissue. Blockages that interfere with thissupply eventually cause the brain tissue to stop functioning. If thedisruption in supply occurs for a sufficient amount of time, thecontinued lack of nutrients and oxygen causes irreversible cell death(infarction). Accordingly, immediate medical treatment of an ischemicstroke is critical for the recovery of a patient. To access the cerebralvasculature a physician typically advances a catheter from a remote partof the body (typically a leg) through the vasculature and into thecerebral region of the vasculature. Once within the cerebral region, thephysician deploys a device for retrieval of the obstruction causing theblockage. Concerns about dislodged obstructions or the migration ofdislodged fragments increases the duration of the procedure at time whenrestoration of blood flow is paramount. Furthermore, a physician mightbe unaware of one or more fragments that dislodge from the initialobstruction and cause blockage of smaller more distal vessels.

Many physicians currently use stents to perform thrombectomy (i.e. clotremoval) to resolve ischemic stroke. Typically, the physician deploysthe stent into the clot, in an attempt to push the clot to the side ofthe vessel and re-establish blood to flow. Tissue plasminogen activator(“Tpa”) is often injected into the bloodstream through an intravenousline. The TPA must travel in the blood stream until it reaches the clotthat is causing the blockage. Once the Tpa contacts the clot, it beginsto break up the clot with the hope of restoring blood flow to theaffected areas. Tpa is also often administered to supplement theeffectiveness of the stent. Yet, if attempts at clot dissolution areineffective or incomplete, the physician can attempt to remove the stentwhile it is expanded against or enmeshed within the clot. In doing so,the physician must effectively drag the clot from the vessel, in aproximal direction, into a guide catheter located within vessels in thepatients neck (typically the carotid artery). While this procedure hasbeen shown to be effective in the clinic and easy for the physician toperform, there remain some distinct disadvantages using this approach.

The stent may not sufficiently hold onto the clot as it drags the clotto the cathter. In such a case, the clot might not move from the vessel.Another risk is that use of the stent might mobilize the clot might fromthe original blockage site, but the clot might not adhere to the stentduring translation toward the catheter. This is a particular risk whentranslating through bifurcations and tortuous anatomy. Furthermore,blood flow can migrate the clot (or fragments of the clot) into abranching vessel at a bifurcation. If the clot is successfully broughtto the guide catheter in the carotid artery, yet another risk is thatthe clot may be “stripped” or “sheared” from the stent as the stententers the guide catheter. Regardless, simply dragging an expanded stent(either fully or partially expanded) can result in undesired trauma tothe vessel. In most cases, the stent is oversized compared to thevessel. Dragging a fixed metallic (or other) structure can pull thearteries and/or strip the cellular lining from the vessel, causingfurther trauma such as a hemorrhagic stroke (leakage of blood from acerebral vessel). Also, the stent can become lodged on plaque on thevessel walls resulting in further vascular damage.

In view of the above, there remains a need for improved devices andmethods that can remove occlusions from body lumens and/or vessels.While the discussion focuses on applications in the cerebralvasculature, the improved devices and methods described below haveapplications outside of the area of ischemic stroke.

SUMMARY OF THE INVENTION

The examples discussed herein show the inventive device in a form thatis suitable to retrieve obstructions or clots within the vasculature.The term obstructions may include blood clot, plaque, cholesterol,thrombus, naturally occurring foreign bodies (i.e., a part of the bodythat is lodged within the lumen), a non-naturally occurring foreign body(i.e., a portion of a medical device or other non-naturally occurringsubstance lodged within the lumen.) However, the devices are not limitedto such applications and can apply to any number of medical applicationswhere elimination or reduction of the number of connection points isdesired.

The devices discussed herein include interventional medical devices forretrieving and securing an obstruction within a vessel lumen. In oneexample the device comprises an elongated stent comprising a pluralityof struts, the stent being collapsible for positioning in the catheterduring delivery and having an expanded profile such that when expandedthe struts are configured to engage the obstruction; a shaft fixedlyattached to the elongated stent and having a flexibility to navigatethrough tortuous anatomy; a fluid permeable cover having a distal endcoupled to a proximal end of the elongated stent a cover wall defining acavity and extending along the shaft, and a proximal end being moveablerelative to the shaft, where the fluid permeable cover is collapsiblefor positioning in the catheter during delivery and is expandable upondeployment from the catheter such that a portion of the fluid permeablecover is expandable; and where the fluid permeable cover is axiallypliable such that when the device is deployed in the vessel andfrictional forces are applied against the fluid permeable cover,proximal movement of the shaft and elongated stent cause inversion ofthe fluid permeable cover wall such that the fluid permeable cover walleverts over the elongated stent.

In one example, the device includes a configuration where the eversiblecover, capturing structure, and shaft are a unitary structure. Thedevice can also be configured so that each wire located at an end of thefree section loops back to the cover causing the wires at the end of thefree section to be continuous.

Another variation of the device includes a capturing structureconfigured to engage the obstruction for removal from the vessel lumen;a shaft fixedly attached to the capturing structure and having aflexibility to navigate through tortuous anatomy; a fluid permeablecover having a distal end coupled adjacent to a proximal end of thecapturing structure, a cover wall defining a cavity and extending alongthe shaft, and a proximal end being moveable relative to the shaft,where the fluid permeable cover is collapsible for positioning in thecatheter during delivery and is expandable upon deployment from thecatheter such that a portion of the fluid permeable cover is expandable;and where the fluid permeable cover is axially pliable such that whenthe device is deployed in the vessel and frictional forces are appliedagainst the fluid permeable cover, proximal movement of the shaft andcapturing structure cause inversion of the fluid permeable cover wallsuch that the fluid permeable cover wall everts over the capturingstructure.

In another variation, the disclosure includes a method of securing anobstruction within a vessel. In one example, the method comprisespositioning a catheter within a vessel; advancing a shaft having anobstruction removal device affixed thereto out of the catheter;advancing an eversible cover out of the catheter such that a fixed endof the eversible cover is adjacent to a proximal end of the obstructionremoval device and a free end of the eversible cover is moveablerelative to the shaft and obstruction removal device; expanding at leasta portion of the eversible cover against a portion of a wall of thevessel; allowing the obstruction removal device to become at leastpartially enmeshed with the obstruction; and proximally translating theshaft and obstruction removal device with at least a portion of theobstruction affixed thereto such that resistance of the eversible coveragainst the vessel resists movement of the eversible cover causing thefree section of the eversible cover to evert over the proximallytranslated obstruction removal device.

In another variation at least a portion of the cover wall adjacent tothe distal end has a set shape that is everted upon expansion. Thedevice can also optionally include a catheter body, where in a deliveryconfiguration, the shaft, capturing structure and eversible cover arelocated within the catheter body and where the capturing structure isadvanceable in and out of a distal end of the catheter body.

The device can also be configured so that the fixed section of theeversible cover comprises a pre-set shape to reduce a force required toevert the evertable cover.

The retrieval devices can comprise any number of capturing or retrievaldevice such as a filter, an artherectomy device, a rotational cutter, anaspiration device, stent based retrievers and retrieval baskets.

The methods described herein can include methods of securing anobstruction within a vessel. In one example, the method can comprise:positioning a catheter within a vessel; advancing a shaft having aretrieval device affixed thereto out of the catheter; advancing aneversible cover out of the catheter such that a fixed end of theeversible cover is affixed adjacent to a proximal end of the retrievaldevice and a free end of the eversible cover is moveable relative to theshaft and retrieval device; expanding a at least a portion of theeversible cover against a portion of a wall of the vessel; manipulatingthe retrieval device to become at least partially enmeshed with theobstruction; and proximally translating the shaft and retrieval devicewith at least a portion of the obstruction affixed thereto such thatresistance of the eversible cover against the vessel resists movement ofthe eversible cover causing the free section of the eversible cover toevert over the proximally translated retrieval device.

In another variation, the methods can include further withdrawing theshaft from the vessel such that during withdrawal the eversible coverforms a protective barrier over the obstruction to lessen shearingforces caused by the vessel and reduce dislodging portions of theobstruction from the retrieval device.

Another variation of a method includes a method of preparing a retrievaldevice comprising: providing a retrieval device having been previouslyremoved from a body of a patient where the retrieval device includes aprotective cover where a fixed end of the protective cover is affixedadjacent to a proximal end of the retrieval device and where a free endis located distally to the fixed end covering the retrieval device andis moveable relative to the second end; reversing the protective coverby moving the free end proximally of the fixed while the fixed endremains affixed adjacent to the proximal end of the retrieval device;inserting the retrieval device and cover into a catheter where the freeend of the cover is proximal to the fixed end of the cover and retrievaldevice such that upon deployment from the catheter, the free end of thecover deploys proximally to the fixed end of the cover.

In another example, the devices described herein can include medicaldevice retrieval systems for securing an obstruction within a vessellumen and for use with a catheter configured to be navigated through thevasculature. In one variation, the device comprises an elongated stentcomprising a plurality of struts, the stent being collapsible forpositioning in the catheter during delivery and having an expandedprofile such that when expanded the struts are configured to engage theobstruction; a shaft fixedly attached to the elongated stent and havinga flexibility to navigate through tortuous anatomy; a fluid permeablecover having a distal end coupled to a proximal end of the elongatedstent a cover wall defining a cavity and extending along the shaft, anda proximal end being moveable relative to the shaft, where the fluidpermeable cover is collapsible for positioning in the catheter duringdelivery and is expandable upon deployment from the catheter such thatat least a portion of the fluid permeable cover is expandable; where thefluid permeable cover is axially pliable such that when the device isdeployed in the vessel the frictional forces between the vessel and thefluid permeable cover permit proximal movement of the shaft andelongated stent to cause inversion of the fluid permeable cover wallsuch that the fluid permeable cover wall evens over the elongated stent.

Another variation of a device includes an interventional medical devicefor use with a catheter configured for delivery through vasculature forsecuring an obstruction within a vessel lumen. For example, the devicecan comprise a shaft having a flexibility to navigate through tortuousanatomy, the shaft having a distal portion and a proximal portion; acapturing device comprising a sidewall, the capturing device fixedlylocated at a distal portion of the shaft and having a reduced profilefor positioning in the catheter and an expanded profile, such that upondeployment from the catheter, the capturing device expands to force aportion of the sidewall into the obstruction to at least partiallyattach to the obstruction; a cover having a distal end coupled adjacentto a proximal end of the capturing structure, a proximal end and a coverwall extending therebetween, where the proximal end of the cover isslidable relative to the distal end, where the cover is expandable suchthat when located in the catheter the cover is in a reduced deliverystate and upon advancement from the catheter the cover expands with theproximal end located proximally of the distal end, where the cover wallis compliant such that when deployed from the catheter and the shaft ispulled in a proximal direction frictional forces between the vessel andthe cover wall or proximal end cause the cover to invert as the coverwall inverts over the capturing device to surround the capturing device.

Another variation of the device includes an interventional medicaldevice for securing a retrieval device having one or more obstructionslocated therein for removal from a body. In one such example the medicaldevice includes a sheath having a flexibility to navigate throughtortuous anatomy, the sheath a distal portion and a proximal portion anda lumen extending therethrough; an eversible cover having a fixedsection affixed to the distal portion of the sheath, a free sectionextending in a proximal direction from the fixed section and a coverwall extending from the fixed section to the free section, where theeversible cover is expandable, the eversible cover being axiallycompliant such that when the retrieval device is positioned through thesheath lumen moved in a proximal direction against the eversible cover,the eversible cover everts over the retrieval device allowing for thefree section of the cover to be distal to the retrieval device.

Another variation of the method includes advancing a shaft having aretrieval device affixed thereto to the obstruction; advancing aprotective device over the shaft, the protective device comprising asheath having an eversible cover, where a fixed end of the eversiblecover is affixed to a distal portion of the sheath and a free end of theeversible cover is located proximal to the fixed end; positioning thefixed end of the eversible cover adjacent to the retrieval device andexpanding at least a portion of the eversible cover against a portion ofa wall of the vessel; proximally translating the shaft and retrievaldevice with at least a portion of the obstruction affixed thereto suchthat resistance of the eversible cover against the vessel resistsmovement of the eversible cover causing the free section of theeversible cover to evert over the proximally translated retrievaldevice.

The capturing portions described herein can include a stent retrievaldevice for expanding against one or more occlusive bodies in avasculature. In one example, the stent retrieval device includes anelongate shaft having a flexibility to navigate through tortuousanatomy, the elongate shaft having a distal portion and a proximalportion; a plurality of filaments that diverge from the distal portionof the elongate shaft to form an expandable elongated stent body havinga open distal end and a fluid permeable closed proximal end and a cavitytherebetween, where divergence of the filaments at the distal portion ofthe elongate shaft forms the fluid permeable closed proximal end; wherethe plurality of filaments extending along the shaft are free of anyconnection joints in the distal portion to permit increased flexibilityof the distal portion as it navigates though tortuous anatomy; and oneor more connection joints proximal to the distal portion where theconnection joints secure the plurality of filaments to the shaft.

The stent retrieval can also include at least one of the plurality offilaments that comprise at least two wires twisted together, theelongated stent body further comprising at least one intersection offilaments, where the wires of each filament are interwoven to provideincreased outward radial strength of the elongated stent body and suchthat the wires slide relative to each other as the elongated stent bodyexpands or compresses in diameter to reduce a force required tolinearize the elongated stent body.

The stent retrieval device can have an exterior surface of the elongatedstent body that comprises an irregular surface formed by intersection offilaments.

The stent retrieval device can also have intersection of filamentscomprising a barb or knuckle and where a plurality of barbs or knucklesis radially spaced about the elongated stent body. The stent retrievaldevice can also have an intersection of filaments that comprises a barbor knuckle and where a plurality of barbs or knuckles is aligned with anaxis of the elongated stent body.

In one variation of the devices described herein, the device comprises amain bundle or group of wires that diverge to form a device havingvarious shapes but few or no connections points or joints (wherefabrication of such a construction is referred to as “jointless”).Clearly, the inventive devices described herein are not limited to sucha jointless construction. Additional variation includes one or moreleading wires that are attached to a capturing portion as describedbelow.

Devices of the present invention can incorporate any number of wires ofdifferent characteristics including, but not limited to, materials,shapes, sizes and/or diameters. Clearly, the number of permutations ofdevice configurations is significant. Providing devices with such acomposite construction allows for the manipulation of the device'sproperties to suite the intended application.

As noted herein, the joint-less construction improves the flexibilityand strength of the device by eliminating joints, connection points, orother attachment points. In addition, the joint-less constructionimproves the ability of the device to be delivered through a smallmicrocatheter. As a result, the device and microcatheter are able toaccess remote regions of the vasculature.

The devices may be fabricated to be self-expanding upon deployment froma catheter. Alternatively, the devices can be constructed fromshape-memory alloys such that they automatically deploy upon reaching apre-determined transition temperature.

It should be noted that in some variations of the invention, all or someof the device can be designed to increase their ability to adhere to theobstruction. For example, the wires may be coupled to an energy source(e.g., RF, ultrasonic, or thermal energy) to “weld” to the obstruction.Application of energy to the device can allow the surrounding portion todeform into the obstruction and “embed” within the obstruction.Alternatively, the device can impart a positive charge to theobstruction to partially liquefy the obstruction sufficiently to allowfor easier removal. In another variation, a negative charge could beapplied to further build thrombus and nest the device for better pullingforce. The wires can be made stickier by use of a hydrophilicsubstance(s), or by chemicals that would generate a chemical bond to thesurface of the obstruction. Alternatively, the filaments may reduce thetemperature of the obstruction to congeal or adhere to the obstruction.

Additional devices and methods for treating ischemic stroke arediscussed in commonly assigned U.S. patent application Ser. Nos.11/671,450 filed Feb. 5, 2007; 11/684,521 filed Mar. 9, 2007; 11/684,535filed Mar. 9, 2007; 11/684,541 filed Mar. 9, 2007; 11/684,546 filed Mar.9, 2007; 11/684,982 filed Mar. 12, 2007, 11/736,526 filed Apr. 17, 2007,11/736,537 filed Apr. 17, 2007, 11/825,975 filed Sep. 10, 2007;12/344,378 filed Dec. 26, 2008, 13/012,727 filed Jan. 24, 2011, and13/226,222 filed Sep. 6, 2011; the entirety of each of which isincorporated by reference. The principles of the invention as discussedherein may be applied to the above referenced cases to produce devicesuseful in treating ischemic stroke. In other words, the wire-shapedconstruction of devices according to present invention may assume theshapes disclosed in the above-referenced cases when such a combinationis not inconsistent with the features described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Each of the following figures diagrammatically illustrates aspects ofthe invention. Variation of the invention from the aspects shown in thefigures is contemplated.

FIG. 1 illustrates an example of a device according to the presentinvention when used in a system for removing obstructions from bodylumens.

FIGS. 2A to 2C illustrate working ends of various coverable retrievaldevices.

FIGS. 2D and 2E show variations of retrieval devices.

FIG. 2F shows an independent eversible cover on a delivery sheath.

FIGS. 3A to 3C illustrate an example of a coverable retrieval devicewhere the cover everts about the retrieval structure.

FIG. 4A to 4I illustrates an example where an improved retrieval devicewith passive protection retrieves a clot from tortuous anatomy.

FIGS. 4J and 4K illustrate examples of an obstruction or other materialcaptured within a retrieval device with a cover further protecting theloaded retrieval device.

FIG. 5A illustrates a retrieval device having a retrieval structureadjacent to a double layer cover.

FIG. 5B shows a funnel with a free end that tapers down about thedelivery wire.

FIGS. 5C and 5D show a fixed end of a cover that is pre-shaped to reducethe force required to evert the cover wall.

FIG. 5E shows alternate variation of a passive cover integrated into aretrieval device.

FIG. 5F illustrates a cover having a pre-set flattened cover wall at afixed end of the retrieval structure.

FIGS. 5G to 5I illustrate various layered covers.

FIG. 5J shows a cover that is constructed directly onto the retrievalstructure rather than the delivery shaft.

FIGS. 5K and 5L show a variation of a cover and retrieval device wherethe cover is first mounted in a distal direction and then inverted in aproximal direction.

FIGS. 6A to 6L illustrate a variation of covers for use as describeherein.

FIGS. 7A to 7C show additional variations of covers.

FIG. 8 illustrates a variation of a proximal and distal end of anadditional retrieval device.

FIGS. 9A to 9C illustrate wires of different constructions within adelivery wire or shaft.

FIGS. 10A to 10E illustrate additional variations of covers for use asdescribed above.

FIGS. 11A to 11C illustrate additional variations of covers for use withthe devices and methods described herein.

FIGS. 12A to 12F illustrate various stent designs for increasing theability of a stent to adhere to an occlusion within a vessel.

FIG. 12G illustrates a proximal end of the stent structure.

DETAILED DESCRIPTION

It is understood that the examples below discuss uses in the cerebralvasculature (namely the arteries). However, unless specifically noted,variations of the device and method are not limited to use in thecerebral vasculature. Instead, the invention may have applicability invarious parts of the body. Moreover, the invention may be used invarious procedures where the benefits of the method and/or device aredesired.

FIG. 1 illustrates a system 10 for removing obstructions from bodylumens as described herein. In the illustrated example, this variationof the system 10 is suited for removal of an obstruction in the cerebralvasculature. As stated herein, the present devices and methods areuseful in other regions of the body including the vasculature and otherbody lumens or organs. For exemplary purposes, the discussion shallfocus on uses of these devices and method in the vasculature.

It is noted that any number of catheters or microcatheters maybe used tolocate the catheter/microcatheter 12 carrying the obstruction removaldevice 200 at the desired target site. Such techniques are wellunderstood standard interventional catheterization techniques.Furthermore, the catheter 12 may be coupled to auxiliary or supportcomponents 14, 16 (e.g., energy controllers, power supplies, actuatorsfor movement of the device(s), vacuum sources, inflation sources,sources for therapeutic substances, pressure monitoring, flowmonitoring, various bio-chemical sensors, bio-chemical substance, etc.)Again, such components are within the scope of the system 10 describedherein.

In addition, devices of the present invention may be packaged in kitsincluding the components discussed above along with guiding catheters,various devices that assist in the stabilization or removal of theobstruction (e.g., proximal-assist devices that holds the proximal endof the obstruction in place preventing it from straying during removalor assisting in the removal of the obstruction), balloon-tipped guidecatheters, dilators, etc.

FIG. 2A illustrates a working end of a coverable retrieval device 100.Typically, the device includes a capturing or retrieval structure 200.In the illustrated example, the retrieval structure 200 comprises anelongated stent structure. However, unless specifically noted, thecapturing structure can comprise any number of devices, including butnot limited to a filter, an artherectomy device, a rotational cutter, anaspiration catheter.

The retrieval structure 200 is located at a distal end of a deliverywire 202. In one variation, the retrieval structure 200 can bepermanently affixed to the delivery wire 200 by such methods including,but not limited to adhesive bonding, soldering, welding, polymerjoining, or any other conventional method. In some variations, theretrieval device 200 can be formed from one or more wires forming thedelivery wire 202 or shaft 202. The delivery wire 202 can havesufficient column strength such that it can axially advance and retractthe device 100 within the vasculature as the physician manipulates anon-working end of the delivery wire 202 outside of the body.Accordingly, the delivery wire 202 should have a length that issufficient to extend from the target area, e.g., the cerebralvasculature, to the entry point on the body. Alternatively, additionalvariations of the device 100 can allow for the use of a support memberor catheter that positions the retrieval structure 200 as needed.Additional features of the retrieval structure 200 can be found in thecommonly assigned patents and applications cited herein an incorporatedby reference.

The coverable retrieval device 100 further includes a cover 300 (alsoreferred to as a funnel or sheath) affixed relative to a proximal end206 of the retrieval structure 200. By being affixed relative to aproximal end 206, a distal end 204 of the retrieval structure 200 canmove relative to the cover 300 so that the cover 300 everts over theproximal end 206 of the structure 200 when the cover 300 is expandedwithin a vessel and as the structure 200 is withdrawn into the distalend 302 of the cover 300. This mechanism is discussed in detail below.

FIGS. 2B and 2C illustrate alternative variations of a coverableretrieval device 100. As shown in FIGS. 2B and 2C, the distal end 302 ofthe cover 300 can be spaced from the proximal end 206 of the retrievalstructure 200. Alternatively, the distal end 302 of the cover 300 canextend over a portion of the retrieval structure 200. In somevariations, at least a section of the cover 300 expands to a greaterdiameter than a diameter of the retrieval structure 200. This allows thecover 300 to expand to a vessel wall where the vessel holds the coverstationary while the device is pulled proximally through the cover toevert the cover. In alternate variations, the cover 300 expands to thesame or lesser diameter than the retrieval structure 200 or otherdevice.

FIG. 2D shows a retrieval device 100 with a catheter 112 (usually amicrocatheter). The retrieval device 100 can comprise a single unitarydevice of a cover 300 and retrieval structure 200 (in this case theretrieval structure is an elongated stent structure). One benefit of aunitary device is that additional devices complicates the procedure andcan increase the duration of what is ordinarily a time sensitiveprocedure. The retrieval device 100 can be positioned through thecatheter 112 that includes a hub 114. As a result, the physician onlyneeds to manipulate the unitary retrieval device 100 and thecatheter/microcatheter 112. The retrieval device 100 is loaded into thecatheter 112 for placement at the target site. In addition, theretrieval device can be reloaded if the procedure must be repeated. Thecover 300 and retrieval structure 200 described herein can comprise anyconstruction described herein or as known by those skilled in the art.

FIG. 2E shows a retrieval device 100 with a cover 300 and retrievaldevice 200 with a radiopaque marker 305 therebetween. As shown,variations of the device 100 do not require a catheter or microcatheter.

FIG. 2F illustrates an eversible cover 300 located on a sheath 330having a lumen 332 extending therethrough. A separable retrieval device200 can be coupled to the cover 300 and sheath 330 by inserting the wire202 of the cover retrieval device 200 through the lumen 332 of thesheath 330. In this variation, the eversible cover 300 can be used withany number of different interventional tools. The separate devices canbe assembled prior to delivery into the patient. Alternatively, thedevices can be positioned within the body and subsequently joined oncethe retrieval device 200 engages the target area.

FIG. 3A illustrates an example of a coverable retrieval device 100 wherethe cover 300 is in the process of everting about the retrievalstructure 200. As shown, arrow 50 illustrates a force applied on thewire 202 in a proximal direction. Arrows 52 illustrate a resistanceforce applied by the friction of the expanded cover 300 against a vesselor similar wall. This friction force 52 prevents or resists proximalmovement of the free end 304 of the cover 300 while the fixed end 302moves in a proximal direction with the proximal end 206 of the retrievalstructure 200. This action causes a wall 306 of the cover 300 to evertover the retrieval structure 200. Ultimately, and as shown in FIG. 3B,the free end 304 of the cover 300 ends up distally over the fixed end302. As shown, the wall of the everted cover 300 provides a safety typecover for the retrieval device 200. In additional variations, the fixedend 302 of the cover can actually be slidable or moveable along thedelivery wire 202. However, the similar principle as discussed aboveshall apply to cause everting of the cover 300 over the retrievalstructure 200.

FIG. 3C illustrates another variation of a coverable retrieval device100 after the cover 300 is everted about the retrieval structure 200. Inthis variation, the free end 304 of the cover 300 ends up distally ofthe fixed end 302 and tapers or collapses towards the free end 304. Thecover 300 can be shape set so that prior to eversion the cover is asshown above where the forces acting on the cover wall 306 expandoutwards, but after eversion the forces on the cover wall 306 cause thetapering or collapsing as shown in FIG. 3C.

In accordance with the illustrations discussed above, the cover 300 canbe made so that the cover wall 306 is atraumatic when dragged across alumen wall. The cover can be manufactured from any number of materialsincluding a fabric, a reinforced fabric, a braid, weave, or any suchmaterial that allows for expansion against a wall of the body lumen orvessel as well as to allow evening of a wall 306 of the cover over theretrieval device 200. The cover wall 306 can also comprise combinationsof these materials such as braids of polymer material with metal fibers,soft braids with coil reinforcements or various other combinations.

The cover wall can comprise a mesh that can include any medicallyacceptable materials such as a Nitinol braid. Furthermore, the meshallows for flow through the vessel or lumen while expanded. However,additional variations of the device can include a solid layer ofmaterial substituted for the mesh. Moreover the cover can comprise anynumber of configurations. For example, the cover can comprise a singlelayer wall or a multi layer wall, the open end of the cover could bemade to have terminated ends such as by using continuous wire loopsformed during the braiding process. Alternatively, the ends can be cutand then terminated by encasing in polymer, laser welds, or by foldinginward for a discreet length and then terminating

In one example, the cover 300 comprises a continuous wire constructionas described in earlier commonly assigned patent applicationsincorporated by reference. In one variation the cover 300 comprises afinely braided wire, such as 48-96 wires of 0.0005″ to 0.002″ diameterfine Nitinol wire or similar. Additionally, the wire can comprise cobaltchromium, stainless steel, or similar, or drawn filled tube (dft) withplatinum core. In additional variations, a flat wire or oval wire can beused. The wire does not need to be uniform. Instead, a number ofdifferent types of wires can be used. Some of the individual wires couldbe platinum alloys for added radiopacity.

FIG. 4A to 4I illustrates an example where an improved retrieval device100 with passive protection retrieves a clot 2 from tortuous anatomy.FIG. 4A illustrates a clot 2 that obstructs blood flow in a vessel 6. Asnoted herein, the vessel 6 can comprise any vessel in cerebralvasculature, coronary or peripheral vasculature. Alternatively, thedevice and methods for use are not limited to use in the vasculature.Variations of the principles, concepts, method and devices describedherein can be applicable wherever a retrieval device can be used. FIG.4A also illustrates a guide sheath or access catheter 108 that isadvanced within the vessel. During a procedure, the physician willadvance the access catheter 108 as far distally as possible. However,due to the size of the access catheter 108, a physician typicallypositions it a distance away from the obstruction 2. As shown, there canbe any number of bifurcations 8 in the vessel 6 located between theaccess catheter 108 and the obstruction 2. As discussed herein, in somevariations, the access catheter 108 can be used to remove theobstruction 2 from the body once the obstruction is captured by aretrieval device. However, the greater the distance between the initiallocation of the obstruction 2 and the location of the access catheter108, the greater the risk that the obstruction 2 can break free from theretrieval device or become dislodged due to anatomic or environmentalfeatures, including but not limited to bifurcations, the wall of thelumen, the tortuousity of the anatomy, vessel wall plaque, etc.

FIG. 4B illustrates an optional catheter 112 that advances from theaccess catheter 108 to the site of the obstruction 2. Once at the site,the catheter 112 can deploy a retrieval device (not shown in FIG. 4B) sothat the retrieval device can engage the clot 2. Alternatively, thecatheter 112 can traverse the obstruction 2 as shown in FIG. 4C anddeploy a portion of the retrieval device 100 distally to the obstruction2. The physician then manipulates the retrieval device 100 to secure theobstruction 2. For example, the physician can deploy the retrievalstructure 200 distally to the obstruction 6 and withdraw the retrievalstructure 200 proximally to secure the obstruction 2. In anothervariation, the physician can position the retrieval structure 200 withinthe catheter 2 while the catheter 112 is through or adjacent to theobstruction 2. Then, the physician can withdraw the catheter 112 toexpose the retrieval structure 200 so that it secures to the obstruction2 after expansion. In the illustrated example, the retrieval structure200 comprises an elongated stent type structure that expands (or isexpanded) to enmesh or secure to the obstruction. Although notillustrated, the system can include a distal capture filter or basket asdescribed in any of the commonly assigned applications incorporated byreference herein.

Next, as shown in FIG. 4E, the physician can further withdraw thecatheter 112 to expose a cover 300 as described above. In many cases,the physician exposes the cove 300 once the retrieval structure 200 isengaged with the obstruction 2. This sequential process allows foreasier repositioning of the retrieval structure 200 if necessary.Alternatively, the cover 300 can be deployed prior to engaging theretrieval structure 200 with the obstruction 2. If necessary, thephysician can apply a proximal force on the delivery wire 202 whilewithdrawing the catheter 112 to prevent inadvertent movement of theobstruction 2 and retrieval device 200.

FIG. 4F illustrates the stage with a fully exposed the cover 300 and acatheter 112 moved closer towards the access sheath 108. As shown, thefree end 304 of the cover 300 is proximal to fixed end 302 of the cover300. As also noted above, the cover 300 can be a shape memory alloy thatexpands against the walls of the vessel 6 upon reaching bodytemperature. Alternatively, the cover 300 can be self expanding upondeployment into the vessel 6. In some variations, the cover wall 306comprises a porous material or construction that allows blood tocontinue to flow through the cover 300.

In addition, some variations of the retrieval device 100 include a cover300 that has at least a section that expands to a greater diameter ordimension than the retrieval structure 200. This allows for expansion ofthe cover 300 against the wall of the vessel 6. In most variation,expansion of the cover 300 provides sufficient friction against thewalls of the vessel to overcome column strength of the cover walls 306allowing for everting of the cover walls 306 over the retrievalstructure 200 and obstruction 2 as discussed herein. As noted above, inalternate variations the cover 300 can expand a diameter or dimensionthat is equal to or less than the retrieval structure 200.

FIG. 4G illustrates proximal movement of the delivery wire 202, whichcauses proximal translation of the obstruction 2 and retrieval structure200. Because the cover 300 is expanded against the walls of the vessel 6the free end 304 of the cover 300 does not move or moves less than thefixed end 306 of the cover 300. The fixed end 306 moves with theobstruction 2 and retrieval structure 200 in a proximal directioncausing the cover walls 306 to evert over the obstruction 2 andretrieval structure 200. Unlike a conventional funnel, the evening coverfunctions similar to a conveyor belt type movement as the obstructionand retrieval structure move together. This action allows for a passivetype of protection since cover 300 does not need to be actuated over theobstruction 2 and retrieval structure 200 and can be performed in aquick manner by simply withdrawing the deployed retrieval device 100.

FIG. 4H illustrates a stage where the fixed end 306 of the cover 300 isnow proximal to the free end 304. As shown, the everted cover 300 formsa protective sheath or cover over the obstruction 2 and the retrievalstructure 200. FIG. 4H also illustrates how the cover 300 protects theobstruction 2 and retrieval structure 200 as they are pulled along thevessel and navigate the tortuous anatomy, walls of the vessel, as wellas bifurcations 8. The cover 300 and cover wall 306 also protects thevasculature from the surface of the retrieval structure 200 andobstruction 2.

FIG. 4I shows the obstruction 2 and retrieval structure 200 protected bythe cover 300 as the retrieval device 100 is positioned against orwithin the access catheter 108 in preparation for removal from the body.The retrieval device 100 can remain outside of the access catheter 108as the physician removes both devices from the body. Alternatively, thecover 300 can assist in pulling the retrieval device 100 and obstruction2 into the access catheter 108 by compressing the obstruction 2 as it ispulled into the access catheter 108.

FIGS. 4J and 4K illustrate examples of an obstruction or other material2 captured within a retrieval device 2 with a cover 300 furtherprotecting the loaded retrieval device 200.

FIGS. 5A to 5K show a variety of cover configurations. FIG. 5Aillustrates a retrieval device 100 having a retrieval structure 200adjacent to a double layer cover 300 with an exterior wall 306 and aninterior wall 308.

FIG. 5B shows a cover 300 with a free end 304 that tapers down about thedelivery wire 202 where the cover 300 will eventually form a double wallconfiguration when the cover 300 everts over the retrieval structure200. The tapered free end 304 limits the cover 304 from moving once theretrieval structure 200 reaches the free end 304 thereby forming doublewall protection over the retrieval structure 200.

FIGS. 5C and 5D show how a fixed end 302 of a cover 300 can bepre-shaped to reduce the force required to evert the cover wall 306 orto lower the threshold to trigger passive covering of the retrievalstructure by the cover.

FIG. 5E shows alternate variation of a passive cover 300 integrated intoa retrieval device 100. In this variation, the retrieval device 100includes a control shaft or wire 202 to manipulate the working end ofthe retrieval device 100. The cover 300 floats along the shaft 202between two fixed anchors or nodes 220, 222. The cover 300 can float orslide between the fixed nodes 220, 222. The nodes 220, 222 can compriseradiopaque marker bands, glue joints, or any other mechanicalobstructions capable of stopping the translation of cover 300. When thedevice 100 advances through a microcatheter, the rear or proximal node220 limits rearward movement of the cover 300. When positionedappropriately, the microcatheter can be withdrawn to expose theretrieval device 200 and cover 300 as described herein. When theretrieval structure 200 engages the obstruction (not shown) theretrieval device 100 can be withdrawn by pulling on the delivery shaft202. While this occurs, the cover 300, being expanded against the vesselremains stationary (or moves at a slower rate than the obstruction andretrieval structure 200 due to the friction against the vessel wall).The retrieval structure 200 and clot enter the cover 300, causing thedistal node 222 to make contact with the near end 320 of the cover 300.This contact causes the retrieval structure 200 and cover 300 totranslate as an integrated unit. It should be appreciated that the covercould be a single layer or double layer cover, and could have any of thewire design variables and termination variables described herein.

FIG. 5F illustrates a cover having a pre-set flattened cover wall 304 ata fixed end 302 that is spaced from a proximal end of the retrievalstructure 200. FIGS. 5G to 5I illustrate various layered covers 300. Thelayered covers allow for shortening the axial length of the cover andtherefore shortens the required translation length. Layering of thecover wall 306 allows for a shortened deployed length of the cover 300when deployed in the vessel or body structure. As the cover 300 evertsover the retrieval structure 200 the layered wall 306 extends. As aresult, shortening the length reduces the length that the cover 300extends into the proximal vessels and reduces the length of that theretrieval structure 200 must travel to become protected by the cover300. This also helps shorten the distance required to move the device100 to complete eversion of the cover 300.

FIG. 5J shows a cover 300 that is constructed directly onto theretrieval structure 200 rather than the delivery shaft 202. Thisconstruction also assists in reducing the distance necessary to completepassive protection of the retrieval structure by the cover.

FIG. 5K show a variation of a cover 300 that is mounted in a distaldirection over the retrieval device 200 and then everted in a proximaldirection over the wires or shaft 202 as shown by arrows 230. Onceeverted, as shown by FIG. 5L, the device 100 is ready for deployment asdiscussed herein.

FIGS. 6A to 6B illustrate a variation of a cover 350 for use as describeherein. Additionally, the cover 350 can be used with any obstructionretrieval device not limited to the retrieval baskets and stentsdescribed herein. The covers 350 disclosed herein can be used where thephysician desires to shield the obstruction being removed from thefrictional effects of the arteries or from the local anatomy (e.g.,branching vessels, tortuous anatomy, or other substances on the vesselwalls). In use, the covers can be sized for use with guide catheters,micro-catheters, and/or distal access catheters. The covers can includeany number of radiopaque marker bands to allow non-invasive imaging ofthe device (see marker 390 affixed between cover 350 and shaft 212 inFIG. 7B as one example). In any case, once the retrieval device capturesa clot or obstruction, as described above, the device and clot areprotected by the cover so that the cover eliminates or reduces directcontact between the interior of the wall of the vessel and the clot.

FIGS. 6A to 6C show a variation in which a cover is created from one ormore mesh tubes 372. FIG. 6B illustrates inversion of the tube 372 sothat a first end 374 is drawn over the tube 372 towards a second end376. As shown in FIG. 6C, this creates a double walled cover having anexterior wall 378 separated from an interior wall 380. In one example,such a spacing or gap could range between 0.001 inches to 0.100 inches.However, any range is contemplated within alternative variations of thedevice. In some variations the inverted cover 350 is heat set tomaintain a separation between layers or walls 378 380 of the cover 350.Typically, if the cover 350 is not created from a radiopaque material, amarker band will be placed on the proximal end 376 and adjacent to ashaft or catheter to which the cover 350 is attached. In some variationsthe construction of the mesh material is compliant to allow for movementof a first part of the mesh relative to a second part of the meshthrough compression and expansion of the mesh material. In such a case,the individual strands forming the mesh are moveable relative to oneanother to cause the mesh to be naturally compliant. Accordingly, thisconstruction permits the inner wall 380 to move or deflect with theretrieval device and/or obstruction as the device is withdrawn into thecover 350. In some variations, both ends of the mesh 374 and 376 areaffixed to the catheter, shaft or wire.

In many variations, the cover mesh is selected to minimize friction whenthe interior layer 380 moves against the exterior layer 378. Forexample, the braid pattern, wire, wire diameter, angle of the braid andor other features can be selected to reduce friction between the outerlayer 378 and inner layer 380. This permits the inner layer 380 to moveproximally with a retrieval device while the outer layer remainsstationary. Again, as discussed above, the construction of the meshpermits compression and expansion of the mesh layer to permit movementof the inner layer while the outer layer remains affixed when engagedagainst the vessel wall. In certain variations, the cover is heat set sothat the inner layer has cushioning and the ability to deflect to assistin movement of the inner layer. FIG. 5C also illustrates a coer 350having a tapered design.

FIGS. 6D to 6L illustrate additional variations of cover construction toproduce covers having more than two walls. For example, a mesh tube 372is everted or drawn over a second end 376 in the direction 420. As shownin FIG. 6E this produces a dual layer cover having a open ends 422 and424 and a folded end 426. The dual layer tube is then folded over againin the direction 420. This creates a cover construction with an exteriorlayer 378 and an interior layer 380 as well as a first intermediatelayer 381 and a second intermediate layer 383. As shown in FIG. 6F, thecover can be set to assume the tapered shape having an opening at thefirst end 374 that is flared with the ends of the mesh at the second end372, which are ultimately affixed to a shaft, wire or other catheterdevice as described herein.

FIG. 6G illustrates another example of a cover construction. As shown, afirst mesh tube 372 is placed coaxially with a second tube 372. Theconcentric tubes are then everted in direction 420 to produce a fourlayer cover. As shown in FIG. 6H, the cover can comprise an interiormesh layer 380, and exterior mesh layer 378 as well as any number ofintermediate layers 381, 383 depending on the number of tubes that areinitially used. The second end 372 of the cover 350 includes fourunconnected ends of the mesh tubes that can be affixed to a shaft ortube as discussed herein, while the first end 374 of the cover 350 canbe shape set to taper from the opening.

FIGS. 6I to 6L illustrate another example of the construction of amulti-wall cover. As shown in FIG. 6I, a first end 374 of a mesh tube372 is everted over and beyond a second end 376 in direction 420 toproduce the configuration of FIG. 6J. Next, the first end 374 is evertedor folded back in direction 420 to produce the configuration of FIG. 6K.Finally, the first end 374 is folded again in direction 420 so that theends 374 and 376 are even to produce the cover configuration shown inFIG. 6K. Again, one end of the cover 350 can be set to form the taperedshape while the other respective end can be affixed to a catheter orshaft.

Although the covers of the present disclosure are presented withoutadditional structures, it should be noted that these covers are coupledwith a shaft or other member so that the cover can be advanced withinthe target anatomy to assist in removal of a device, structure, ordebris from the site.

FIGS. 7A to 7C show addition variations of covers 350. FIG. 7Aillustrates a cover in which the cover wall as defined by the innerlayer 380 and outer layer 378 is set in a shape that varies along alength of the cover. For example, the end adjacent to the cover opening382 can be set to a bulbous shape. Such a configuration assists inmaintaining separation of layers 378 and 380, which aids in re-entry ofthe retrieval device. Additional configurations of cover walls that varyin thickness are within the scope of this disclosure.

One of the benefits of using a cover 350 as described herein is that thecover reduces flow through the vessel when deployed so that theretrieval device can remove the obstruction without the full force ofthe flow of blood opposing the obstruction. Typically, conventionaldevices relied upon the use of an inflated balloon to obstruct flow.However, use of a cover eliminates the need for total occlusion of bloodflow. FIG. 7B illustrates a further improvement on a cover 350 that aidsin flow reduction. As shown, the cover 350 includes a dense region 386and a relatively less dense region 384. This configuration permitsgreater blood flow through the region 385 while region 386 reduces orprevents blood flow. Furthermore, the distal section of the cover ismore flexible and conformable. Additional mesh layers can be added toany of the cover designs to alter flow characteristics or even providereinforcement to the cover. Alternatively, or in combination, the braiddensity can be altered to adjust the porosity of the braid at differentsections. Furthermore, additional braid layers can also be used toaffect porosity of portions of the cover or even the entire cover.Deployment of a cover can reduce blood flow by 30% to 40%. Addingadditional layers or coatings can additionally reduce flow.

FIG. 7C shows another variation of a cover 350 in which the meshpartially or totally is obscured using a polymeric coating 388 thatreduces the permeability of the mesh design. Furthermore, drugs or othersubstances can be placed within the cover wall of any of the covers orcan be deposited on the cover using the polymeric coatings. In someexamples, the covers described herein can range from a length of 10 mmup to 50 mm. The OD at the opening of the cover can range from 7 mm andcould range between 4 mm to 10 mm. Again, any range of dimensions iscontemplated within the disclosure.

The covers described herein can further be stacked on a device. Forexample, two or more covers can be placed on a device to provide addedprotection.

The cover/rentry devices described herein can be constructed of anymaterial currently used in vascular applications, including thosediscussed above. Furthermore, fabrication of the cover from a DFTmaterial can provide additional benefits as the entire cover remainsradiopaque and can be imaged non-invasively. Furthermore, the covers canbe provided with any type of medicament or bioactive substance either ina polymer that coats the mesh or in a delivery agent within the mesh orbetween layers. Such substances include tpa, urokinase, IIb/IIIainhibitors, and other clot disruptors or inhibitors.

FIG. 8 illustrates another variation of a retrieval device 400 includinga distal capture portion 426 coupled to one or more leading wires in theform of a main bundle 402. The main bundle extends through a sheath 106that includes a proximal capture portion 460. The configuration of theretrieval device 400 can incorporate the proximal and distal captureportions discussed herein as well as various other configurationsdiscussed in the commonly assigned patent applications noted above.

An end 464 of the proximal capture portion 460 is affixed to a distalend of the sheath 106. However, as noted above, other variations arewithin the scope of the disclosure. The main bundle 402 can optionallyterminate at a handle 442. As noted above, in certain variations, themain bundle is joined to a stiffer wire or stiffer bundle of wires. Thisallows the device 400 to have a very flexible distal section with arelatively stiffer proximal section. The device 400 can have a proximalbundle 403 that comprises either the exposed wires or a covering/tubeover the wires. In certain variations, the bundle or wire 402, 403 canbe encapsulated with a coating. The device also includes a cover 300adjacent to the retrieval device.

The proximal end of the sheath 106 includes a sheath handle 444. Asdiscussed herein, axial movement of the bundle 402 or proximal bundle403 (typically at the handle 442) results in movement 126, ortranslation of the bundle within the sheath 106. This action moves thedistal capture portion 426 (as shown by arrows 126). In certainvariations, the device 400 is loaded into a microcatheter (not shown butdiscussed above) that is delivered to the site of the obstruction andcrosses the obstruction.

In some variations, the sheath hub 444 includes one or more locking hubs446. Where actuation (either axial or rotational) of the locking hub 446locks the main bundle 402 relative to the sheath handle 444 and sheath106. It follows that such locking action also locks the distal captureportion 426 relative to the proximal capture portion 460. A variety ofmethods can be employed to increase a frictional interference betweenthe locking hub 446 and the proximal bundle 403. As a result, when aphysician determines a length of an obstruction, the physician can set aspacing between the capturing portions 426 460 by locking the proximalbundle 403 relative to the sheath hub 444. Accordingly, the proximalbundle 403 can include any type of incremental markings to allow thephysician to readily determine a spacing of the capturing portions. Asillustrated, the sheath hub 444 can include additional injection portsto deliver fluid or other substances through the sheath 106.

As noted above, the device 400 can be used with a micro-catheter. Inthose variations it is important that the device 400 is loaded withoutdamaging the distal bundle 402, capture portions 426 460, and/or sheath106. As a result, the device 400 can include an optional cover 486 thatreduces the proximal capture portion 460 (and or the distal captureportion 426) for loading within the microcatheter and/or sheath 106.

Another variation of the device 400 includes an insertion tool 480slidably affixed to the sheath 480. Because variations of the device 400can be extremely flexible, the insertion tool 480 can be used to providecolumn strength to the sheath 106, bundle 402 or other components as thedevice 400 is pushed into the microcatheter. The insertion toolcomprises a rigid section 482 and a frictional coupler 484. The rigidsection 282 has a column strength that supports the device 400 toprevent buckling. The frictional coupler 484 can be a flexible materialthat allows an operator to squeeze or grip the coupler 484 to create atemporary frictional interface between the loading tool 480 and thedevice 400 (typically the sheath 106). Such an action allows axialadvancement of the device 400 as the loading tool 480 is advanced intothe microcatheter. Once the rigid section 482 is fully inserted into themicrocatheter, the operator releases the frictional coupler 484 and canwithdraw the loading tool 480 from the catheter without withdrawing thedevice 400. The insertion tool 480 can also include an optional loadingtube 486 slidably coupled to the rigid section 482. When used, the cover486 can withdraw the proximal and distal capturing portion 226 260within the loading tube 486. The loading tube 486 then couples to amicrocatheter allowing the capturing portions to advance therein as therigid section 482 and frictional coupler 484 advance the device 400relative to the loading tube 486.

FIGS. 9A to 9C show cross sectional views taken along the line 9A-9A inFIG. 2A. As shown, the wire form construction described herein allowsfor a number of configurations depending on the particular application.For example, the individual wires 254 (as discussed herein) maythemselves comprise a bundle of smaller wires or filaments. In addition,the wires can be selected from materials such as stainless steel,titanium, platinum, gold, iridium, tantalum, Nitinol, alloys, and/orpolymeric strands. In addition, the wires used in a device may comprisea heterogeneous structure by using combinations of wires of differentmaterials to produce a device having the particular desired properties.For example, one or more wires in the device may comprise a shape memoryor superelastic alloy to impart predetermined shapes or resiliency tothe device. In some variations, the mechanical properties of selectwires can be altered. In such a case, the select wires can be treated toalter properties including: brittleness, ductility, elasticity,hardness, malleability, plasticity, strength, and toughness.

The device may include a number of radiopaque wires, such as gold andplatinum for improved visibility under fluoroscopic imaging. In otherwords, any combination of materials may be incorporated into the device.In addition to the materials, the size of the wires may vary as needed.For example, the diameters of the wires may be the same or may vary asneeded.

In addition, the individual wires may have cross-sectional shapesranging from circular, oval, d-shaped, rectangular shape, etc. FIG. 9Aillustrates one possible variation in which a number of circular wires254 are included around another larger wire 256. Moreover, the device isnot limited to having wires having the same cross-sectional shape orsize. Instead, the device can have wires having differentcross-sectional shapes. For example, as shown in FIG. 9B, one or morewires 256 can have a different cross-sectional shape or size than areminder of the wires 254. Clearly, any number of variations is withinthe scope of this disclosure. This construction can apply to theretrieval portion, capturing portion and/or the covering portion of thedevice.

To illustrate one such example, a device can have 8-12 wires made of0.003″ round superelastic material (e.g., Nitinol). The device mayadditionally have 2-4 wires made from 0.002″ platinum for fluoroscopy.Of the 8-12 Nitinol wires, 1-4 of these wires can be made of a largerdiameter or different cross-section to increase the overall strength ofthe device. Finally, a couple of polymer fibers can be added where thefibers have a desired surface property for clot adherence, etc. Such acombination of wires provides a composite device with properties notconventionally possible in view of other formation means (such as lasercutting or etching the shape from a tube or joining materials withwelds, etc.). Clearly, any number of permutations is possible given theprinciples of the invention.

In another example, the device may be fabricated from wires formed froma polymeric material or composite blend of polymeric materials. Thepolymeric composite can be selected such that it is very floppy until itis exposed to either the body fluids and or some other deliveredactivator that causes the polymer to further polymerize or stiffen forstrength. Various coatings could protect the polymer from furtherpolymerizing before the device is properly placed. The coatings couldprovide a specific duration for placement (e.g., 5 minutes) after whichthe covering degrades or is activated with an agent (that doesn't affectthe surrounding tissues) allowing the device to increase in stiffness sothat it doesn't stretch as the thrombus is pulled out. For example,shape memory polymers would allow the device to increase in stiffness.

In another variation, one or more of the wires used in the device maycomprise a Drawn Filled Tube (DFT) such as those provided by Fort WayneMetals, Fort Wayne, Ind. As shown in FIG. 9C, such a DFT wire 252comprises a first material or shell 258 over a second material 260having properties different from the outer shell. While a variety ofmaterials can be used, one variation under the present devices includesa DFT wire having a superelastic (e.g., Nitinol) outer tube with aradiopaque material within the super-elastic outer shell. For example,the radiopaque material can include any commercially used radiopaquematerial, including but not limited to platinum, iridium, gold,tantalum, or similar alloy. One benefit of making a capturing portionfrom the DFT wire noted above, is that rather than having one or moremarkers over the capturing portion, the entire capturing portion can befabricated from a super-elastic material while, at the same time, thesuper-elastic capturing portion is made radiopaque given the core ofradiopaque material within the super-elastic shell. Clearly, anycomposite DFT wire 252 can be incorporated into the system and capturingportions described herein.

Another aspect applicable to all variations of the devices is toconfigure the devices or portions thereof that engage the obstruction toimprove adherence to the obstruction. One such mode includes the use ofcoatings that bond to certain clots (or other materials causing theobstruction.) For example, the wires may be coated with a hydrogel oradhesive that bonds to a thrombus. Accordingly, as the device securesabout a clot, the combination of the additive and the mechanicalstructure of the device may improve the effectiveness of the device inremoving the obstruction. Coatings may also be combined with thecapturing portions or catheter to improve the ability of the device toencapsulate and remove the obstruction (e.g., a hydrophilic coating).

Such improvements may also be mechanical or structural. Any portion ofthe capturing portion can have hooks, fibers, or barbs that grip intothe obstruction as the device surrounds the obstruction. The hooks,fibers, or barbs 370 can be incorporated into any portion of the device.However, it will be important that such features do not hinder theability of the practitioner to remove the device from the body.

In addition to additives, the device can be coupled to an RF or otherpower source (such as 14 or 16 in FIG. 1), to allow current, ultrasoundor RF energy to transmit through the device and induce clotting or causeadditional coagulation of a clot or other the obstruction.

FIGS. 10A to 10E illustrate additional variations of covers 300 for useas described above. For example, as show in FIG. 10A, a cover 300 cancomprise a single wire, coil, or laser cut tube 350. Alternatively, asshown in FIG. 10B, the cover 300 can comprises two or more 350, 352wires or coils. FIG. 10C shows a cover 300 comprising a coil 350 insidea mesh structure 354. A variation of the device shown in FIG. 10C caninclude a compliant atraumatic mesh 354 that is radially supported bythe coil (whether interior or exterior to the mesh). The coil 350provides the outward force against the vessel. FIG. 10D illustrates apolymeric film or membrane 356 coupled to a coil 350. The polymeric film356 can be permeable to fluid flow or impermeable. FIG. 10E illustratesa dual layer braid construction having an inner braid 358 and an outerbraid 360. The braids can be constructed to have unique properties. Forexample, the inner braid 358 can be composed of fewer wires or largerdiameter wires, such that it provides an expansion force against thevessel wall. The outer braid 360 can comprise a softer construction andincreased compliance. Accordingly, it can be comprised of a number ofsmaller diameter wires having a denser pattern to provide increasedsurface area to protect the obstruction as it is removed from the body.Alternatively, these two constructional elements (e.g., braids ofvarying diameters) can be combined into a single layer or even multiplelayers for the cover.

FIG. 11A illustrates yet another variation of a device 100 having aretrieval structure 200 and cover 300 where the cover is simplyfabricated from the same material as the retrieval structure so long asit functions as described herein. The variation can optionally includeone or more barbs 370 to increase resistance against a vessel wall.

FIGS. 11B and 11C illustrate a variation where the cover 300 comprises aballoon material. FIG. 11B illustrates the balloon cover 370 prior todeployment. FIG. 11C illustrates the balloon cover 370 once deployed.

The retrieval devices described herein can optionally comprise elongatedstents 400 as shown in FIGS. 12A to 12E. These stents 400 can includeany number of features to better assist the stent 400 in becomingenmeshed into the obstruction. For example, FIG. 12A illustrates avariation of a stent 400 affixed to a shaft 412. As noted herein, theshaft 412 can include a lumen extending therethrough. Alternatively, theshaft 412 can include a solid member with the stent 400 affixed to adistal end thereof. The variation shown in FIG. 12A includes a stentwhere a distal end 414 that is “closed off” by intersecting elements orwires 402 403. Accordingly, any of the variations of the stentsdisclosed herein can include an open lumen type stent or a closed lumentype stent as shown in FIG. 12A. As noted herein, the wires forming thestent 400 can comprise a single wire that is wound from a firstdirection (e.g., from proximal to distal) and then wound back in asecond direction (e.g., from distal to proximal).

FIG. 12A also illustrates a stent 400 comprised of twisted wires 402 orelements. For example, FIG. 12B shows a magnified view of the section12B in FIG. 12A. As illustrated, the elements 402 403 are twisted toincrease the surface area at the exterior perimeter of the stent 400.The twisting or spiraling of the elements 402 403 creates additionalsurface area to increase the ability of the stent 400 to capture debris,thrombus, foreign body, etc. as the stent is expanded against thedebris. The twisting elements 402 403 can twist along the entire lengthof the stent 400 or along one or more portions of the stent. In certainvariations, the twisting of the elements 402 403 is sufficiently loosesuch that as the stent expands into a clot or obstruction, the twistedpairs slightly separate to allow material to become trapped between theelements making up the pairs. The construction shown in FIGS. 12A and12B also provide an additional benefit to a retrieval stent. In theillustrated variation, the twisted or spiraling elements interlock withcrossing elements to form intersections 405 that provided added radialexpansive force. As shown, a first twisted element 407 passes in betweenelements 402 403 of an intersecting element 409. When in an expandedstate, the element on the interior of the intersection 405 (in this caseelement 403) provides an added outward radial force against theintersection 405. However, since the elements are not affixed butinstead are slidable at the intersection 405, the force required tolinearlize and compress the stent 400 is reduced due to the fact thatthe intersections are not affixed but slidable over the adjacentelements. This reduced linearization force allows the stent to becompressed to a small diameter for positioning within a microcatheterbut allow for a significant radial expansive force once removed from themicrocatheter. This design allows for a reduction in radial force of thestent against the vessel wall when the stent is pulled and removed fromthe vessel. However, this design also provides a high degree of radialforce due to the interweaving of elements when the stent is deployed inthe vessel prior to withdrawal of the stent.

FIGS. 12C to 12F illustrate another variation of types of stents 400that have an irregular surface at an exterior of the stent 400 that isformed by an intersection of elements 402 403. The intersection orcrossing of the elements forms a type of barb or knuckle 416 thatcreates an irregular surface on the exterior of the stent 400. FIG. 12Cillustrates a variation of a stent 400 having a plurality of knuckles 52that are radially spaced about an axis 390 of the stent 400. FIG. 12Eshows another variation of a stent 400 with knuckles 416 aligned with anaxis 390 of the stent 400 as shown in FIG. 12D. Although the figuresshow the axial and radial aligned knuckles 416 on separate devices, bothtypes of knuckles 416 can be incorporated into a single stent structure.Varying the alignment of knuckles can permit increased radial force asthe stent expands into the obstruction or increased flexibility as thestent navigates through tortuous anatomy.

FIG. 12G illustrates a proximal end of the stent structure 400 as shown,a plurality of elements 402 and 403 extend along the shaft 412 anddiverge to form the fluid permeable closed proximal end of the stentstructure 400. The elements 402 and 403 that extend along the shaft 412can be covered by a sheath, tube, spiral cut tube, or any structure 418that prevents separation of the elements 402 403. A variation of thestent structure 402 includes a construction where the elements 402 403are not glued, welded, or have any similar type of joint in the distalportion 420 of the shaft 412. Instead, the joint 411 is located proximalto the distal section of the shaft 412 in an intermediate section 422.Because joints or other similar features reduce flexibility of thejoined structure, positioning the joints 411 in a proximal area allowsthe distal portion 420 of the shaft to remain flexible.

The methods described herein may also include treating the obstructionprior to attempting to remove the obstruction. Such a treatment caninclude applying a chemical or pharmaceutical agent with the goal ofmaking the occlusion shrink or to make it more rigid for easier removal.Such agents include, but are not limited to chemotherapy drugs, orsolutions, a mild formalin, or aldehyde solution.

As for other details of the present invention, materials andmanufacturing techniques may be employed as within the level of thosewith skill in the relevant art. The same may hold true with respect tomethod-based aspects of the invention in terms of additional acts thatare commonly or logically employed. In addition, though the inventionhas been described in reference to several examples, optionallyincorporating various features, the invention is not to be limited tothat which is described or indicated as contemplated with respect toeach variation of the invention.

Various changes may be made to the invention described and equivalents(whether recited herein or not included for the sake of some brevity)may be substituted without departing from the true spirit and scope ofthe invention. Also, any optional feature of the inventive variationsmay be set forth and claimed independently, or in combination with anyone or more of the features described herein. Accordingly, the inventioncontemplates combinations of various aspects of the embodiments orcombinations of the embodiments themselves, where possible. Reference toa singular item, includes the possibility that there are plural of thesame items present. More specifically, as used herein and in theappended claims, the singular forms “a,” “and,” “said,” and “the”include plural references unless the context clearly dictates otherwise.

It is important to note that where possible, aspects of the variousdescribed embodiments, or the embodiments themselves can be combined.Where such combinations are intended to be within the scope of thisdisclosure.

We claim:
 1. A medical device retrieval system for securing anobstruction within a vessel lumen and for use with a catheter configuredto be navigated through the vasculature, the device comprising: anelongated stent comprising a plurality of struts, the stent beingcollapsible for positioning in the catheter during delivery and havingan expanded profile such that when expanded the struts are configured toengage the obstruction; a shaft fixedly attached to the elongated stentand having a flexibility to navigate through tortuous anatomy; a coverhaving a distal end coupled to a proximal end of the elongated stent, acover wall defining a cavity and extending along the shaft, and aproximal end being moveable relative to the shaft, where the cover iscollapsible for positioning in the catheter during delivery and selfexpands upon deployment from the catheter such that a portion of thecover expands outward against a vessel wall; and where the cover isaxially pliable such that when the device is deployed in the vessel andfrictional forces are applied against the cover, proximal movement ofthe shaft and elongated stent cause inversion of the fluid permeablecover wall such that the cover wall everts over the elongated stent,where the cover is self-collapsing when inverted.
 2. The medical deviceof claim 1, where the cover, elongated stent, and shaft are a unitarystructure.
 3. The medical device of claim 1, where at least a portion ofthe cover wall adjacent to the distal end has a set shape that iseverted upon expansion.
 4. The medical device of claim 1, furthercomprising a catheter body, where in a delivery configuration, theshaft, elongated stent and eversible cover are located within thecatheter body and where the elongated stent is advanceable in and out ofa distal end of the catheter body.
 5. The medical device of claim 1,where the cover comprises a plurality of layers forming the cover wall.6. The medical device of claim 1, where a free section of the coverpartially restricts about the shaft without being attached to the shaft.7. The medical device of claim 1, where a portion of the cover wallextends distally beyond the distal end when the cover is expanded. 8.The medical device of claim 1 where the distal end of the covercomprises a pre-set shape.
 9. The medical device of claim 1, where thecover is self expanding.
 10. The medical device of claim 1, where aportion of the cover at or adjacent to the distal end comprises abulbous shape.
 11. The medical device of claim 1, where the covercomprises a mesh material.
 12. The medical device of claim 11, where themesh material is constructed from a single continuous wire.
 13. Themedical device of claim 1, where the cover comprises an inner braidedlayer and an outer braided layer, where the outer braided layer isrelatively more compliant than the inner braided layer.
 14. The medicaldevice of claim 1, where the cover is fluid permeable.
 15. The medicaldevice of claim 1, where the cover is configured to compress inwardafter evening and compress the obstruction.
 16. The medical device ofclaim 1, where the cover is configured to taper or collapse towards theproximal end after everting.
 17. A medical device retrieval system forsecuring an obstruction within a vessel lumen and for use with acatheter configured to be navigated through the vasculature, the devicecomprising: a capturing structure configured to engage the obstructionfor removal from the vessel lumen; a shaft fixedly attached to thecapturing structure and having a flexibility to navigate throughtortuous anatomy; a cover having a distal end coupled adjacent to aproximal end of the capturing structure, a cover wall defining a cavityand extending along the shaft, and a proximal end being moveablerelative to the shaft, where the cover is collapsible for positioning inthe catheter during delivery and self-expands upon deployment from thecatheter such that a portion of the cover expands outward against avessel wall; and where the cover is axially pliable such that when thedevice is deployed in the vessel and frictional forces are appliedagainst the cover, proximal movement of the shaft and capturingstructure cause inversion of the fluid permeable cover wall such thatthe cover wall everts over the capturing structure. where the cover isself-collapsing when inverted.
 18. The medical device of claim 17, wherethe capturing structure comprises an elongated stent structure having aplurality of struts, the stent being collapsible for positioning in thecatheter during delivery and having an expanded profile.
 19. The medicaldevice of claim 17, where the distal end of the cover is coupleddirectly to the capturing structure.
 20. The medical device of claim 17,where the distal end of the cover overlaps a portion of the capturingstructure.
 21. The medical device of claim 17, where the distal end ofthe cover is coupled directly to the shaft leaving a gap between theproximal end of the cover and the distal end of the capturing structure.22. The medical device of claim 17, where the capturing structurecomprises a device selected from a group consisting of a filter, anartherectomy device, a rotational cutter, an aspiration device, stentbased retrievers, a balloon and retrieval baskets.
 23. The medicaldevice of claim 17, where the cover is fluid permeable.
 24. The medicaldevice of claim 17, where the cover is configured to compress inwardafter evening and compress the obstruction.
 25. The medical device ofclaim 17, where the cover is configured to taper or collapse towards theproximal end after evening.